Integration of FOC with DFVC for interior permanent magnet synchronous machine drives

In this paper, the drawbacks of the conventional f-t frame based maximum torque per ampere (MTPA) control schemes are analyzed and mathematically proved. In order to inherit the merits of both the direct flux vector control (DFVC) in field weakening region and field orientated control (FOC) in constant torque region while avoiding their disadvantages, an integrated control scheme is proposed. The proposed control scheme integrates the FOC into f-t reference frame at low speeds to achieve a relatively accurate and robust MTPA control, while at high speeds, the DFVC is adopted to utilize the advantages of f-t frame based control scheme in field weakening region. A shape function is utilized by the proposed control scheme to achieve a smooth transition between the two control schemes. The proposed control scheme is verified by experiments under various operation conditions on a prototype IPMSM drive. The simulation and experimental results illustrate that the proposed control scheme could achieve a better MTPA control accuracy in constant torque region and a better field weakening performance in the constant power region. Meanwhile the complex look-up tables for FOC in field weakening region and the difficulties in observing flux vector at low speed are avoided.